The present invention claims a priority based on the Japanese Patent Application No. H11-51489, the contents of which is incorporated hereinto by reference in its entirety.
1. Field of the Invention
This invention relates to a digital camera.
2. Description of Related Art
In a portable battery-driven electric equipment such as a digital camera, the internal resistance of the battery increases gradually in accordance with the use of the equipment, and it becomes impossible to supply necessary power to the equipment when the internal resistance increases to a certain level. A user wishes to use the battery as long as possible. However, a large voltage drop causes an unstable operation of the equipment. Therefore, in a conventional electric equipment, a warning display system and/or a forcible power turn-off process (a battery check process) are employed. For example, Japanese Unexamined Laid-open Patent Publication H9(1997)-130649 discloses an electric still camera in which a voltage drop is detected to display warning and the power is automatically turned off.
Furthermore, in the aforementioned Patent Publication H9-130649, in a case where the equipment has a plurality of operation modes, since the load depends on the mode, different voltages to be subjected to the battery check process are set depending on the mode. According to the aforementioned publication, in a moving image mode the battery check level is set to be higher, while in a still image mode the battery check level is set to be lower.
However, in a conventional digital camera mentioned above, when the battery is consumed, a user cannot recognize a remaining available photographing number, resulting in a poor operability.
In addition, the aforementioned digital camera still includes various problems to be solved regarding how to fully consume the battery effectively.
First, no control considering a battery discharging characteristic has been considered. FIG. 12 illustrates a discharge characteristic of an alkali-manganese battery for use in a portable electric equipment such as a digital camera. In a state that a load is connected to a terminal, the initial terminal voltage is 6.0 V(volt) (when four batteries are connected in series). The terminal voltage decreases along the curve V(t) with time when continuously discharged by connecting to the load. In this embodiment, since the battery check voltage Vth is set to be 3.8 V, the power supply to the equipment is turned off at the timing (time t4) of V(t)=3.8 V.
However, in the course the voltage drop, when there is a power-off time period T caused by a power-off operation by a user or an automatic power-off function, the electromotive force of the battery is restored. In a case where the terminal voltage is V1 at the time immediately before turning off the power, the electromotive force is restored to V2 when the power is turned on immediately after the power-off time period T. However, the voltage suddenly drops to the terminal voltage V1 as shown in the curve Vxe2x80x2 (t). Thereafter, the voltage drops along the curve V(txe2x88x92T) parallel to the curve V(t), delaying by the power-off time period T. At the time of t4+T, the voltage V(txe2x88x92T) comes equal to the voltage Vth and the power is turned off based on the battery check.
As understood from the above, in actual, a portable electric equipment such as a digital camera is used by repeatedly turning on and off, and it can be said that the battery is completely consumed only when the maximum terminal voltage Vth at the time of turning on the power comes to Vth. However, this is not considered by the aforementioned Patent Publication.
As shown in FIG. 12, when a consumed battery is used, since the voltage suddenly drops, the use of the apparatus will be restricted. According to the aforementioned Publication, it merely discloses that a moving mode is prohibited and a still mode is allowed. However, in a case of a digital camera, there are various restrictions regarding, for example, the number of photographing, the use of a flash lamp, turning on/off the monitor display (view finder display), the relationship between the reproduction mode and the photographing mode, the use of automatic focusing mechanism, the execution of the automatic power turn-off process for automatically turning off the power when an operation has not been performed for a predetermined time period, and the execution of an automatic video turn-off process for automatically turning off the power supply to a video circuit or a display circuit of a digital camera. In other words, the battery life depends on how to execute these processing. Therefore, in order to lengthen the battery life, the relationship between the battery voltage and the aforementioned operations should be considered.
It is an object of the present invention to provide an electric equipment including a digital camera in which a battery can be effectively consumed while keeping the battery life as long as possible.
It is another object of the present invention to provide an is electric equipment in which a battery life can be kept long without lowering an operability of the electric equipment.
According to a first aspect of the present invention, a battery-driven electric equipment includes a detector for detecting a voltage of the battery, a calculator for calculating an available photographing number based on the voltage detected by the detector, and an indicator for indicating the available photographing number calculated by the calculator.
With this electric equipment, since the available photographing number is set and displayed on a display portion based on the voltage of the battery detected by the detector, a user can recognize how many photographs can be taken by the camera without lowering the operability even if the voltage of the battery drops.
Furthermore, since the available photographing number is displayed, a user""s positive power saving operation by positively turning off the power can be expected, resulting in an enhanced power saving of the battery and a lengthened battery life.
According to a second aspect of the present invention, a battery-driven electric equipment includes a detector for detecting a voltage of the battery, a manipulation member, a discrimination unit for discriminating whether or not the manipulation member has not been manipulated for a predetermined time period, and a controller for suspending a power supply from the battery when the discrimination unit discriminates that the manipulation member has not been manipulated for the predetermined time period, wherein the controller changes the predetermined time period based on the voltage detected by the detector.
With this electric equipment, in a case where the voltage of the battery drops, wasteful power consumption can be prevented by shortening the predetermined time period causing the power turn-off, resulting in a lengthened battery life.
According to a third aspect of the present invention, a battery-driven electric equipment includes a detector for detecting a voltage of the battery, a plurality of operation modes including at least a reproduction mode for reproducing a recorded image, a selector for selecting any one of the plurality of operation modes, and a controller for controlling a selection of the reproduction mode by the selector based on the voltage detected by the detector.
With this electric equipment, in a case where the voltage of the battery drops, it is possible to prohibit the use of the reproduction mode, resulting in decreased power consumption.
According to a fourth aspect of the present invention, a battery-driven electric equipment includes a detector for detecting a voltage of the battery, a flash lamp for lightening up an object, and a controller for controlling a use of the flash lamp based on the voltage detected by the detector.
With this electric equipment, in a case where the voltage of the battery drops, it is possible to prohibit the use of the flash lamp, resulting in decreased power consumption.
According to a fifth aspect of the present invention, a battery-driven electric equipment includes a detector for detecting a voltage of the battery, a calculator for calculating a remaining available operation time period of the electric equipment based on the voltage detected by the detector, and an indicator for indicating the available operation time period calculated by the calculator.
With this electric equipment, since the available operation time period is displayed, it is possible for a user to recognize how long the electric equipment can be used. Therefore, even if the voltage of the battery drops, the operability of the electric equipment does not deteriorate.
According to a sixth aspect of the present invention, a battery-driven electric equipment includes a detector for detecting a voltage of the battery, a display for displaying an image, and a controller for controlling a use of the display based on the voltage detected by the detector.
With this electric equipment, in a case where the voltage of the battery drops, it is possible to prohibit the use of the display, resulting in decreased power consumption.
According to a seventh aspect of the present invention, a battery-driven electric equipment includes a detector for detecting a voltage of the battery, a first dynamic RAM for storing an image, a display for displaying the image, a second dynamic RAM for displaying the image stored in the first dynamic RAM on the display, and a controller for controlling a power supply from the battery to the second dynamic RAM based on the voltage detected by the detector.
With this electric equipment, in a case where the voltage of the battery drops, it is possible to prohibit the use of the dynamic RAM, resulting in decreased power consumption.
According to an eighth aspect of the present invention, a battery-driven electric equipment includes a detector for detecting a voltage of the battery, a focusing lens, a zoom lens, an automatic focusing mechanism for automatically adjusting a focus of the focusing lens, a discrimination unit for discriminating whether or not a use of the automatic focusing mechanism should be prohibited based on the voltage detected by the detector, an indicator for indicating that it is possible to manually adjust the focus of the focusing lens when the discrimination unit discriminates that the use of the automatic focusing mechanism should be prohibited, and a driver for driving the zoom lens to a predetermined position when the discrimination unit discriminates that the use of the automatic focusing mechanism should be prohibited.
With this electric equipment, in a case where it became impossible to use the automatic focusing mechanism because of the dropped voltage of the battery, it is possible to display on the indicator that the mode is a manual focus mode and to set the zoom lens to a predetermined position.